(1) Field of the Invention
This invention relates to creamy or milky skin cosmetic compositions consisting of oil-in-water emulsions (hereinafter referred to as O/W emulsions) in which an oily substance is dispersed in water with the aid of an emulsifying agent composed of at least one naturally-occurring glycyrrhizic compound and at least one naturally-occurring water-soluble polysaccharide. More particularly, it relates to such skin cosmetic compositions which cause no irritation to the skin, have great safety and affinity for the skin, exhibit excellent storage stability and emulsion stability, and present an attractive appearance (fine texture and good gloss).
(2) Description of the Prior Art
It is well known in the prior art that skin cosmetics of the emulsion type, such as creams and milky lotions, are required to satisfy the following conditions:
(1) They must cause no irritation to the skin and hence have great safety for the skin.
(2) They must have good emulsion stability and storage stability.
(3) They must have good chemical stability including high resistance to hydrolysis.
(4) They must present an attractive appearance from the viewpoints of texture and gloss.
(5) They must have great affinity for the skin.
In order to meet these requirements, elaborate compositional designs are being made, for example, by selection of suitable emulsifying agents, search for useful combinations thereof, and concomitant use of special materials. However, it is not easy to accomplish this purpose. Specifically, it is very difficult to satisfy the above-described conditions by using a single emulsifying agent.
For example, nonionic surface active agents of the polyoxyethylene alkyl ether type are strongly irritative to the skin and poor in emulsifying power. Nonionic surface active agents of the ester type, such as (polyoxyethylene fatty acid esters, polyoxyethylene glycerol-fatty acid esters, polyoxyethylene sorbitan fatty acid esters and the like,) are poor in emulsifying power and resistance to hydrolysis.
Anionic surface active agent, such as sulfuric esters of higher alcohols, alkylarylsulfonic acid salts, and higher fatty acid salts and the like, have a strong degreasing power and cause irritation to the skin.
Cationic surface active agents and ampholytic surface active agents are also irritative to the skin.
On the other hand, dipotassium glycyrrhizinate and monoammonium glycyrrhizinate have only a weak emulsifying power. Thus, creams and milky lotions using these compounds alone are lacking in gloss and remarkably poor in storage stability, as will be described hereinafter.
Karaya gum, locust bean gum, xanthan gum and the like are characterized by thickening properties, but are poor in emulsifying power. Thus, they cannot provide any practical emulsion stability, as will be described later.
Pectin has a somewhat better emulsifying power than karaya gum, locust bean gum, xanthan gum and the like. Nevertheless, the use of pectin alone as emulsifying agent hardly produces emulsions having good emulsion stability and storage stability. U.S. Pat. No. 2,372,159 discloses cosmetic compositions in which an oily substance is dispersed in water by the combined use of a cationic surface active agent (cetyl trimethyl ammonium bromide) and pectin. However, these cosmetic compositions irritate the skin due to the cationic surface active agent.
In order to overcome the above-described difficulties with skin cosmetic compositions of the emulsion type, the present inventors have performed intensive and extensive studies and have discovered that, when an oily substance is dispersed in water by using a combination of a naturally-occurring glycyrrhizic compound and a specific water-soluble polysaccharide in place of a synthetic emulsifier, the synergistic effect of both natural materials brings about remarkable improvements in emulsifying power, emulsion stability, and emulsion homogeneity and thereby provides an O/W emulsion having excellent stability to long-term storage and temperature changes and presenting an attractive appearance (fine texture and good gloss) and, moreover, this emulsion exerts a mild action on the skin without causing irritation thereto and produces a variety of beneficial cosmetic effects. The present invention is based on this discovery.